<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style type="text/css">
*{margin: 0;padding: 0;}
div{
	width: 200px;
	height: 200px;
	margin:0 auto;
	font-size: 30px;
	color: white;
}
div:nth-child(2){
	background: red;
}
div:nth-child(3){
	background: yellow;
}
div:nth-child(4){
	background: pink;
}
div:nth-child(5){
	background: black;
}
img{
	width: 100px;
	position: fixed;
	top:0px;
	left:300px;
}
</style>
<script type="text/javascript"src="jquery-1.9.1.min.js"></script>
<script type="text/javascript">
$(function(){
	$(window).scroll(function(){
       var re = $(window).scrollTop();
       document.title = re ;

       if(re>400){
       	$("img").slideDown(300);
       }else{
       	$("img").slideUp(300);
       }




	})
})
</script>


</head>

<body>
<img src="1.jpg" alt="" />

<div class="dv">1</div>
<div class="dv">2</div>
<div class="dv">3</div>
<div class="dv">4</div>

</body>
</html>
